Process for extracting rare earths from ores and residues



United States Patent PROCESS FOR EXTRACTING RARE EARTHS FROM ORES ANDRESIDUES Howard E. Kren ers, David W. Newman, and Frank C. Kautzky, WestChicago, Ill assignors to American Potash 8; Chemical Corporation, acorporation of Delaw re No Drawing. Application June 20, 1952 eri N9! 117 Claims. (Cl. 2319) This invention relates to certain innovations andimprovernents in processes for extracting rare earths from tires orresidues rich in rare earth fluocarbonates or in the mineral,bastnasite. More particularly, the invention relates to novel processesfor extracting rare earths from such ores or residues wherein either allor a portion of the rare earth values can be obtained directly as agranular, easily filterable precipitate of rare earth fluoride.

The ores may either be refined or they may be crude or semi-refined andcontain variable amounts of mineral bastnasite together with ganguematerials such as calcite, harite fluorspar, silicates, etc.

The'first st'ep in the conventional process for extracting rare. earthsfrom ores and residues, e.g. monazite sands, involves reacting the rareearth ore with concentrated sulfuric acid. The reaction mixture isstirred and heated to. a tjemperature of approximately 230350 C. toconvert the rare earth compounds in the ore into anhydrous rare earthsulfates. The reaction product is then leached water to, dissolve therare earth sulfates and the resulting rare earth solutions were treatedin various ways to obtain desired rare earth salts and compounds.However, the application of such conventional process to bastnasite typeores involves certain difficulties which malge, it objectionable. Thereis excessive frothing; the fluorine has to be eliminated to avoidsubsequent formation of a slimy, gelatinous rare earth fluorideprecipitate; and, additional facilities are required to recover the expelled hydrofluoric acid.

Aceording to the present invention it was found that the mineralbastnasite, which is essentially a rare earth fluocarbonate, and oresand residues rich in bastnasite or rare earth fluocarbonates, could betreated by a new and different process which oifered important andunexpected advantages and savings over the conventional process referredto above.

The term bastnasite as used herein designates broadly the group ofminerals whose composition includes rare earths, fluoride and carbonatein various proportions with or without other constituents. A pure formof bastnasite would be represented by the general formula RPCO where Rdesignates the rare earth elements. There are closely relatedbastnasite-type ores which have a somewhat different or more complexcomposition such, for example, as the mineral parisite. This mineralcontains calcium in addition to the rare earths and has the generalformula 2RFCO .CaCO

' Briefly, the process of the present invention involves firstsubjecting an ore or residue rich in bastnasite or in some other form ofrare earth fluocarbonates, to a roasting operation so as to drive ofi' asubstantial portion of the carbon dioxide content present as thecarbonate. It has been found that during the course of such a roastingstep when it is properly carried out, a substantial portion of thecerium present in the ore or residue is oxidized to the eerie (i.e.tetravalent) state, Furthermore, it appears that the rare earthfluocarbonate constitutent of the ore or residue is converted to rareearth fluo-oxide er a mixture of rare earth fluoride and rareearthogride. The roas ed e taine can e r ad ly and qu ckly dissolvedeven without heating in a dilute non-reducing acid, such as dilutenitric acid or dilute sulfuric acid, and the resulting solutionseparated from the ganglia Q1 insoluble residue. This solution whichcontains substantielly l f he r re e rth. alue of the. raw mat ia isthen treated in one of two ways depending upon whether or not it isdesired to obtain all of the rare, earth values in the for n of theflueride or only a part of them as such. In case it is desired to obtainall of the, rare earth values in the form of the fluoride, the, solutionso obtained is treated with a soluble substance which furnishes fluorideions such as, for example, hydrofluoric acid, or an alkali metalfluoride in suflicientquantity to directly precipitate all of the rareearth value, as a granular, easily filterable fluoride precipitate.

In case only a portion of the rare earth values are desired as thefluoride, then the solution of rare earths is treated with a suitablereducing agent such as sulfur dioxide and this treatment results in theformation of a precipitate of rare earth fluoride leaving the solutionsubstantially fluorine free so that it can be treated in known manner torecover the rare earth values. p

The unroasted ores are generally onlysparingly soluble even in largeexcesses of acid and heating to elevated temperature is necessary inorder to solubilize them.

An important object of the invention is an improved process for theextraction or recovery of rare earths from ores and residues rich inbastnasite or other rare earth fluocarbonates, whichcomprises firstroasting the ore or residue so as to drive otf a substantial portion ofthe carbon dioxide content therefrom and oxidize a large portion of thecerium content to the ceric state, and then treat the roasted ore withacid, preferably a dilute nonreducing acid, so as to dissolve the rare,earth. values from the gangue or insolubles.

An important object of the invention is the provision of an improvedmethod of treating ores and residues rich in bastnasite or rare earthfluocarbonates so as to place them in a highly porous condition wherethey are readily soluble in dilute acid without fine grinding.

Another important object of the invention is theproyision of a processof treating ores and residues richin bastnasite or rare earthfluocarbonates whereby rareearth fluorides can be obtained directly andincidental to the Process of re rin the r e earth. a u sv fr m su h oresand residues.

Another importantobject of the invention is a method Qt eat ng oPIQQQSSL JE; ores. o r siduesri h nbas n s q r a e ea hv fln carb es soa o obtain p ec p ta es o r e th fl o des, ch. aresra u a non-g l tious; easily t v ble a d ot er s cct v nienflynd easi y handled.

An he mportant j t. h nvention is provision of a novel method; ofsolubilizing relafiiYe y in so bl rare ear h fluori es y cond i thesiium con en so a t f rm a c mple h hefi otide p esent which isreadilysoluble inf dilute, acid.

no e mpo an o ject o he nve t on. a ava me h d. of co rin ra a h l s.item ore and residues, rich in bastnasite or rare earthfiuocarbonate iththe es ity f ha n to pel, the fli a de contentv of the ore.

Still a, further object of the invention is-a novel method, of: a g o eand. es dues richas na ite are; e rth fluc aibenatesse as. to par outhe, f uor de; content directly in, the form, of rare earth fluoride,leanng e alanc of the a e ar h valueslin h ere/subs stantially' fluoridefree.

.fornia.

obvious andwill, in part, appear hereinafter.

. For a more complete understanding of the nature and scope of theinvention, reference may now be had to the following detaileddescription thereof wherein illustrative and preferred examples are setforth.

Commercial deposits of bastnasite are, among other places, located inthe States of New Mexico and Cali- Bastnasite from the deposits in NewMexico is .of much higher purity than that available from the depositsin California. While ores from these or other deiposits of bastnasiteare presently the primary raw materials used in the processes of thisinvention, it will be understood that bastnasite ores from otherdeposits may be used and also other ores or residues which are rich inrare earth fluocarbonatcs may also be utilized. The invention is alsouseful in connection with ores and residues containing rare earthfluorides or rare earth fluooxides for the recovery of the rare earthvalues therefrom.

The first step in the recovery of rare earths from an ore rich inbastnasite or a residue rich in rare earth fluocarbonates, after the oreor residue has been cleaned, is to roast the ore or residue so as toeliminate a substantial portion of the carbon dioxide content therefromand oxidize at least a substantial portion of the cerium to the cericstate thereby converting the bastnasite or rare earth fluocarbonate intoa condition such that it may be readily dissolved by a dilute acid. Ingeneral, the ore or residue should be roasted in such a way as toeliminate enough of the carbon dioxide content present as carbonates sothat there will be no objectionable frothing when the roasted materialis treated with the dilute acid. In addition, the roasting also has tobe sufficient to convert an adequate proportion of the cerium from thetrivalent to the tetravalent state so that it will form solublecomplexes with the fluoride present in the ore and with theranion of theacid used for dissolution. However, the roasting must not be excessive,otherwise rare earth oxides will be formed which are refractory (i.e.dead burnt) in nature and highly resistant to attack with acid, andtherefore not readily dissolved. It has also been found that during theroasting operation and as a result thereof the ores or residues acquirea high degree of porosity which further facilitates the rapid solutionof the roasted material in the acid.

The ore or residue may be roasted either batchwise or continuouslydepending upon equipment available and existing facilities andconditions. Commercial type roasting equipment may be utilized. Rotarykilns and furnaces of standard design have been found to be verysatisfactory.

After being roasted the ore or other raw material is subjected totreatment with acid to dissolve the rare earth values therein. Anon-reducing acid is preferably used and commercially this means thatthe choice of acid will usually lie between sulfuric acid and nitricacid. However, in certain instances more expensive acids such asperchloric acid or acetic acid may be used in place of sulfuric ornitric acid. Acid-forming gases, such as sulfur dioxide, may beintroduced into water suspensions of the roasted ores or residues inlieu of using acids themselves. It has been found that the acids may bedilute and usually dilute sulfuric acid or dilute nitric acid will beused because of the advantages in reduced cost, ease of handling, andless expensive equipment required. However, it will be understood thatconcentrated acid may be used if desired. Normally, excessive dilutionis to be avoided because of the increased costs involved in handlinglarge b-ulks of liquid and it is generally desirable to work with rareearth solutions which are as concentrated as practically possible.

It has been found that optimum results may be obtained in reacting theroasted ore or residue with the acid by following somewhat differenttechniques depending upon the particular ores or residues being handled.For example, in some cases it has been found to be desirable to add theroasted material to the mixture of the acid in water. However, in othercases it has been found desirable to first make a slurry of the roastedmaterial in water and then add the acid or an acid-forming substance,e.g. S0 to the slurry. Usually the rate of solution will be suflicientlyrapid and complete so that heating is not required. However, heating maybe used to promote or increase the rate of dissolution and to hasten thereaction with the roasted ore or residue.

Normally, an excess of acid will be used so as to bring aboutpractically complete recovery of the rare earth values and shorten thetime of reaction ad dissolution.

After dissolution of the rare earth values from the roasted ore orresidues, the insolubles consisting largely of non-rare earth materialspresent in the ore or residue may be removed either by settling followedby decanting, or by filtration, and the orange colored solution obtainedmay be further treated as described below to recover the rare earthvalues present therein.

It has been found that when the roasted ore or residue is solubilizedwith either dilute or concentrated acids, the portion of the ceriumwhich was oxidized to the ceric state during roasting remains in theceric state in the aqueous solution obtained by treating the roasted oreor residue with acid, except where acids are used which are capable ofreducing the cerium, such as hydrochloric acid, sulfurous acid or sulfurdioxide. Furthermore, when the properly roasted ore or residue isdissolved in a dilute non-reducing acid, such as nitric or sulfuric, ithas been found that the resulting solution contains not only practicallyall of the rare earths originally present in the ore but alsopractically all the fluoride ions originally present. It is believedthat the fluoride content is held in solution as a soluble cericfluoride complex compound, and it is the formation of such a complexwhich permits the roasted ore or residue to dissolve so readily andeasily even in these dilute acids. The porous structure obtained onroasting increases the area and ease of contact of the acid with the oreand this also promotes easier and faster dissolution.

Ordinarily, when trivalent rare earth fluorides are precipitated fromaqueous solution, the precipitate is a bulky, gelatinous mass which isdifficult to handle and very difficult to filter off. However, it hasbeen found that rare earth fluorides can be precipitated in the form ofa granular, dense, and easily filterable precipitate from the solutionsobtained in the present process by dissolving the roasted ores orresidues in dilute acids.

Certain simple and easily followed precautions with respect to controland technique which are referred to below should be followed for bestresults. The solutions obtained by the acid treatment of the roastedores and residues are treated according to one of the two maintechniques referred to above depending upon the type of products to beobtained. There is a considerable commercial demand and market for rareearth fluorides for use as core ingredients of searchlight carbons andalso for use in steel making. Accordingly, if rare earth fluorides aredesired for these or other purposes, then the rare earth solutionsobtained from the roasted ores or residues are treated by adding theretoa soluble material which furnishes fluoride ions. For example,hydrofluoric acid may be added or sodium fluoride or some other solublefluoride having an unobjectionable cation. Preferably, the solublefluoride is added slowly with agitation.

Upon the addition of the soluble fluoride no precipitate is formed atfirst until a suflicient amount of fluoride ionshas been added .toexceed the complexing .ability of the soluble ceric fluoride complexcompound formed as the result of roasting. However, once this complexingability or capacity has been exceeded, the rare earth fluorides begin toprecipitate and continue to precipitate with the additions of morefluoride ions ,until substantially all of the rare earths present havebeen precipitated. The precipitate is dense and granular and easilyfiltered and managed. The quantity of fluoride added is appreciably lessthan the stoichiometric amount required to combine with the rareearthspr'esent since the fluoride present in the ore or residue itselfis also effective in forming the precipitate.

' In the event-that it is not desired to obtain the maximum amount ofrare earth fluoride from an ore or residue, then the alternate procedureis followed in handling the solutions obtained by the acid treatment ofthe roasted ceric fluoride complex is destroyed, whereupon a precipitateof rare earth fluoride is obtained. This precipitate is dense andgranular and easily filtered and managed as distinguished from the usualbulky, slimy, unmanageable and unfilterable rare earth fluorideprecipitate. By introducing the reducing agent in the proper amounts andin the proper manner, practically all of the fluoride content of thesolution can be removed in the .form of rare earth fluorides leaving asolution or filtrate which contains practically no fluoride. The rareearths remaining in the solution or filtrate will be largely rare earthsulfate or nitrate, depending upon whichof these two acids was used fordissolving the roasted ore or residue. The essentially fluoride-freerare earth solutions can be handled in known manner to recover the rareearths therefrom, as for example, by the precipitation of the rareearths as rare earth sodium sulfate or rare earth oxalate.

The rare earth fluoride precipitate obtained by the reduction, techniqueis not a pure rare earth fluoride but is contaminated with sulfate,nitrate or other anion depending upon the particular acid used and theconditions of precipitation. However, such sulfate or other anion can berather easily removed to provide a rare earth fluoride of commercialquality by treating the precipitate with aqueous hydrofluoric acid,washing the precipitate to remove excess hydrofluoric acid .and sulfuricor nitric acid, filtering the precipitate and drying.

The following illustrative examples will now be given to more fullyacquaint those skilled in the art with practical methods .ofpracticingthe invention.

Example 1 A bastnas'ite-containing ore was processed which analyzed 27%rare earth oxide, 6.6% SiO 3.6% MgO, 6.1% 'CaO, 29.4% BaO, 2.8% M (whereM=Al, Fe, Ti, etc.), 3.1% F, 13% S03, and 10.6% loss on ignition(largely carbonate). The ore was first roasted in a rotary type furnaceat a temperature of about 650 C. until test portions of the roastedproduct showed that no further appreciable loss on ignition occurred.This roasting period required approximately 3 /2 hours. During theroasting step a major portion of the cerium content of the ore wasoxidized to the eerie state and the ore acquired a noticeable porosity.

The roasted ore was then added to a solution of sulfuric acid in waterin the proportions by weight of 400 parts of 66 r-B. sulfuric :acid to1000 parts of water and i000 parts of the roasted 'ore. The mixture wasagitated so as to hasten the dissolution of the rare earths in thedilute acid. After the mixture had been agitated for 6 about 3 hours thesolution was filtered off. The insolubie residue, consisting largely ofthe non-rare earth materials present inthe ore, was washed with 1%sulfuric acid solution and the wash liquor combined with the filtrate.

The filtrate was separated into two approximately equal portions.Aqueous hydrofluoric acid was slowly added to one portion withsuflicient agitation to insure a fairly uniform mixture. Heating fromabout 60 C. to boiling promoted the formation of a granular rare earthfluoride precipitate. At first no precipitate forms but on continuedaddition of the hydrofluoric acid a precipitate of rare earth fluoridebegins to form and settle out. Addition of the hydrofluoric acid iscontinued until a test sample shows that no more rare earth fluorideprecipitate forms, at which point the remaining solution is practicallyfree of rare earths. Since there is a substantial portion of fluoridealready present in the rare earth solution as derived from thebastnasite ore, only suflicient hydrofluoric acid or other solublefluoride needs to be added to complete the formation of rare earthfluoride.

The precipitate of rare earth fluoride obtained may contain up toseveral percent of sulfate ion. By adding an excess of hydrofluoric acidto the reaction mixture containing the precipitate until it smellsdistinctly of hydrofluoric acid and then boiling the solution, thesulfatecontaminated rare earth fluoride may be converted to rare earthfluoride of commercial quality. The precipitate of rare earth fluorideas formed also may be freed of sulfate by filtering off the residualsolution and reslurrying the precipitate with additional hydrofluoricacid. The rare earth fluoride precipitate is granular in nature and iseasily filtered and handled.

The cerium in the rare earth fluoride precipitate is practically all inthe eerie state. If it is desired to have substantially all of thecerium in the cerous state, the precipitate may be treated with areducing agent either before or after separation from the precipitationsolution. Suitable reducing agents for this purpose are sulfur dioxide,oxalic acid, hydrochloric acid, etc.

The second portion of the rare earth solution obtained by dissolving theroasted ore in the dilute sulfuric acid was heated to a temperature ofbetween 40 C. and boiling and sulfur dioxide gas was introduced into thesolution so as to reduce the eerie ions to the cerous state. After asuflicient amount of the sulfur dioxide had been introduced, a rareearth fluoride precipitate began to form and continued to form onaddition of sulfur dioxide until practically all of the fluoride contentof the solution was removed therefrom as the rare earth fluorideprecipitate. The rare earth fluoride so precipitated was very granular,settled well, and was extremely easy tofilter and wash. Such aprecipitate is usually contaminated with various amounts of rare earthsulfate, the extent of contamination depending primarily upon thetemperature at which the precipitation is made. If the precipitationsare made at boiling or near-boiling temperatures, increased amounts ofrare earth sulfate are present in the rare earth fluoride precipitate.due to the inverse solubility of rare earth sulfates with increase intemperature. Accordingly, the amount of rare earth sulfate in .theprecipitate can be reduced by carrying out the precipitation at a lowertemperature of around 40 C. Furthermore, it has been found that theamount of rare earth sulfate in the precipitate can also be reduced bydiluting the rare earth solution obtained by dissolving the roasted orein dilute acid, with either water or with dilute acid before theaddition of the reducing agent so .as to produce a concentration of thesolution such that the rare earth sulfate will not;precipitate from thesolution under the conditions .of heating employed.

After the precipitation of the rare earth fluorides complete, they maybe separated from the solution by filtration or other means and ,thefiltrate will contain largely rare earth sulfate. The rare earth valuescan '7 be recovered from such filtrate by conventional or known methods.For example, the rare earths may be precipitated from the filtrate asrare earth oxalates or as rare earth sodium sulfates, and theseprecipitates may be treated in known and conventional manners to produceother rare earth salts.

In one experiment, one liter of rare earth sulfate filtrate solutionobtained by dissolving roasted ore in dilute sulfuric acid in the mannerdescribed and analyzing 133 grams per liter of rare earth oxide andhaving a density of 27 B., an acidity of 0.6 N H 50 and having 92% ofthe cerium in the ceric state, was heated to 60 C. while stirring.Sulfur dioxide gas was introduced into the solution at the rate of 0.2gram per minute for a period of 50 minutes. At the end of this time thecerium was completely reduced and a granular precipitate of rare earthfluoride was removed by filtration and washed with water. The dryprecipitate weighed 68 grams and analyzed 67.3% rare earth oxide(including 31.9% CeG 16.9% F, and 8.0% S The filtrate containedpractically no fluoride.

Certain modifications and variations may be made in carrying out theprocess as described in the foregoing example. First of all, withrespect to the roasting of the ore, the roasting temperature may rangefrom approximately 400 to 800 C. The exact temperature and degree ofroasting in any instance will depend upon several factors including thenature of the particular ore being processed, the type of equipmentavailable and the time limits on the roasting operation. The amounts ofacid and water used to dissolve the roasted ore may be varied withinrather wide limits but it is usually desired for practical purposes tohave the rare earth solution obtained as concentrated as possible so asto reduce the bulk of the solution that has to be handled and workedwith. While concentrated acids, such as sulfuric or nitric, may beemployed so as to still further minimize the bulk of the solutionshandled, it has been found economical and practical to normally employeither dilute sulfuric or dilute nitric acid. The mixture of acid andwater and roasted bastnasite may be either hot or cold, and if asufficient excess of acid is used, the dissolution of the rare earthvalues will be complete in a period of time ranging from a few minutesto two or three hours depending upon conditions and nature of the ore.

Instead of using hydrofluoric acid as the fluoride ion furnishingmaterial for precipitating rare earth fluoride, other soluble fluoridesmay be used, such as sodium fluoride or the less soluble calciumfluoride.

Many other reducing agents besides sulfur dioxide may be used incarrying out the phase of the process wherein the solution of roastedbastnasite ore is handled so as to precipitate its fluoride content suchas starch, sugars, oxalic acid, carbon and carbonaceous materials,metals such as iron and zinc, reducing acids such as hydrochloric acidand formic acid, hypo, sulfites, thiosulfates, and hydrogen peroxide.

Example 2 A sample of the roasted ore obtained in accordance withExample 1 above was slurried with water and sulfur dioxide gas wasbubbled into the slurry until the slurry was saturated and there was nofurther dissolution of rare earths. After introduction of the S0 hadgone part way a precipitate of rare earth fluoride began to form. At theend of the experiment there was an in soluble portion consisting of rareearth fluoride precipitate and residue from the ore, and a solubleportion comprising a solution of rare earth sulfate. The rare earths inboth portions can be separated or recovered in known manner.

While the invention is largely useful in connection with the processingof ores containing bastnasite, it may also be used in processing variousresidues which may be 'rich in rare earth fluocarbonates and whichtherefore correspond generally to bastnasite.

The discovery that ceric or tetravalent cerium forms soluble complexeswith fluoride and additional anions, such as the sulfate and nitrateanions, may be employed in other connections than in the extraction ofrare earth values from bastnasite ores or residues rich influocarbonates. Another such use is illustrated by the followingexample:

Example 3 A residue containing a substantial quantity of rare earthfluoride is treated with ceric sulfate in a solution of sulfuric acid.The rare earth fluoride dissolves in such a solution apparently due tothe complexing capacity of the ceric ion. The rare earth fluoride maythen be precipitated from the resulting solution by the addition of areducing agent, such as hydrogen peroxide, which reduces the cerium tothe cerous state. Alternately, hydrofluoric acid or some other solublefluoride may be added to precipitate the rare earth fluoride. In eithercase, the precipitate of rare earth fluoride obtained is granular and isvery easy to filter and wash.

In view of the foregoing disclosure, those skilled in the art will beable to carry out the processes of the invention according to theexamples set forth above or with such variations and modifications aswill be readily apparent. Therefore, it will be understood that allmatter describw above is to be interpreted as illustrative and not in alimiting sense.

What is claimed as new is:

l. The process of extracting rare earth metal values from a materialrich in a substance selected from the group consisting of bastnasite andcerium-containing rare earth fluocarbonates which comprises the steps ofroasting such a material to drive ofi a substantial portion of carbondioxide therefrom and oxidize at least part of the cerium, and treatingthe roasted material with a non-reducing acid so as to dissolve the rareearth metal values of the material.

2. The process of extracting rare earth metal values from a materialrich in a substance selected from the group consisting of bastnasite andcerium-containing rare earth fluocarbonates which comprises the steps ofroasting such a material to drive olf a substantial portion of carbondioxide therefrom and oxidize at least part of the cerium, and treatingthe roasted material with a dilute non-reducing acid so as to dissolvethe rare earth metal values of the material.

3. The process of extracting rare earth metal values from a materialrich in a substance selected from the group consisting of bastnasite andcerium-containing rare earth fluocarbonates which comprises the steps ofroasting such a material to drive off a substantial portion of carbondioxide therefrom and oxidize at least part of the cerium, and treatingthe roasted material with sulfuric acid so as to dissolve the rare earthmetal values thereof.

4. The process of extracting rare earth metal values from a materialrich in a substance selected from the group consisting of bastnasite andcerium-containing rare earth fluocarbonates which comprises the steps ofroasting such a material to drive off a substantial portion of carbondioxide therefrom and oxidize at least part of the cerium, and treatingthe roasted material with nitric acid so as to dissolve the rare earthmetal values of the material.

5. The process of extracting rare earth metal values from a materialrich in a substance selected from the group consisting of bastnasite andcerium-containing rare earth fluocarbonates which comprises the steps ofroasting such a material to drive off a substantial portion of carbondioxide therefrom and oxidize at least part of the cerium, and treatingthe roasted material with dilute sulfuric acid so as to dissolve therare earth metal values of the material.

6. The process of extracting rare earth metal values from a materialrich in a substance selected from the group consisting of bastnasite andcerium-containing rare earth fluocarbonates which comprises the steps ofroast ing such a material to drive off a substantial portion of carbondioxide therefrom and oxidize at least part of the cerium, and treatingthe roasted material with dilute nitric acid so as to dissolve the rareearth metal values of the material.

7. The process of extracting rare earth metal values from a materialrich in a substance selected from the group consisting of bastnasite andcerium-containing rare earth fluocarbonates which comprises the steps ofroasting such a material to drive off a substantial portion of carbondioxide therefrom and oxidize at least part of the cerium, treating theroasted material with a non-reducing acid so as to dissolve the rareearth metal values of the material, and adding a water soluble fluorideto the resulting solution of rare earth metal values to obtain an easilyfilterable precipitate of rare earth fluoride.

8. The process of claim 7 wherein the water soluble fluoride is added ina suflicient amount to substantially completely precipitate the rareearth metal values of said solution.

9. The process of extracting rare earth metal values from a materialrich in a substance selected from the group consisting of bastnasite andcerium-containing rare earth fluocarbonates which comprises the steps ofroasting such a material to drive off a substantial portion of carbondioxide therefrom and oxidize at least part of the cerium, treating theroasted material with a dilute nonreducing acid so as to dissolve therare earth metal values of the material, and adding a water solublefluoride to= the resulting solution of rare earth metal values to obtainan easily filterable precipitate of rare earth fluoride.

10. The process of extracting rare earth metal values from a materialrich in a substance selected from the group consisting of bastnasite andcerium-containing rare earth fluocarbonates which comprises the steps ofroasting such a material to drive E a substantial portion of carbondioxide therefrom and oxidize at least part of the cerium, treating theroasted material with dilute sulfuric acid so as to dissolve the rareearth metal values of the material, and adding a water soluble fluorideto the resulting solution of rare earth metal values to obtain an easilyfilterable precipitate of rare earth fluoride.

11. The process of extracting rare earth metal values from a materialrich in a substance selected from the group consisting of bastnasite andcerium-containing rare earth fluocarbonates which comprises the steps ofroasting such a material to drive off a substantial portion of carbondioxide therefrom and oxidize at least part of the cerium, treating theroasted material with dilute nitric acid so as to dissolve the rareearth metal values of the material, and adding a water soluble fluorideto the resulting solution of rare earth metal values to obtain an easilyfilterable precipitate of rare earth fluoride.

12. The process of extracting rare earth metal values from a materialrich in a substance selected from the group consisting of bastnasite andcerium-containing rare earth fluocarbonates which comprises the steps ofroasting such a material to drive off a substantial portion of carbondioxide therefrom and oxidize at least part of the cerium, treating theroasted material with a non-reducing acid so as to dissolve the rareearth metal values of the material, treating said resulting solution ofrare earth metal values with a reducing agent capable of reducing cericcerium so as to precipitate rare earth fluoride therefrom, andseparating the substantially fluoride-free filtrate from the rare earthfluoride precipitate.

13. The process of extracting rare earth metal values from ores rich inbastnasite which comprises roasting the ore to drive 01f a substantialamount of carbon dioxide therefrom and impart a porous structure to theore and oxidize at least a portion of the cerium, treating the roastedore with an excess of dilute sulfuric acid so as to dissolve the rareearth metal values, separating the resulting solution of rare earthmetal values from the insoluble material, and adding to the solution asubstance capable of furnishing fluoride ions in an amount suflicient toprecipitate substantially the entire content of rare earth metal valuesas rare earth fluoride.

14. The process of extracting rare earth metal values from ores rich inbastnasite which comprises roasting the ore to drive 01f a substantialamount of carbon dioxide therefrom and impart a porous structure to theore and oxidize at least a portion of the cerium, treating the roastedore with an excess of dilute sulfuric acid so as to dissolve the rareearth metal values, separating the resulting solution of rare earthmetal values from the insoluble material, and adding to the solution afluoride compound selected from the group consisting of hydrofluoricacid, alkali metal fluorides and alkaline earth fluorides in an amountsufficient to precipitate substantially the entire content of rareearths as rare earth fluoride.

15. The process of extracting rare earth metal values from ores rich inbastnasite which comprises roasting the ore to drive off a substantialamount of carbon dioxide therefrom and impart a porous structure to theore and oxidize at least a portion of the cerium, treating the roastedore with an excess of dilute sulfuric acid so as to dissolve the rareearth metal values, separating the resulting solution of rare earthmetal values from the insoluble material, introducing sulfur dioxideinto the solution to produce a precipitate of rare earth fluoride,sufficient sulfur dioxide being added so that practically all of thefluoride content of the solution is consumed in said precipitate, andseparating the rare earth fluoride precipitate from the remainingsolution of rare earth metal values.

16. The process of extracting rare earth metal values from a materialrich in a substance selected from the group consisting of bastnasite andcerium-containing rare earth fluocarbonates which comprises the steps ofroasting such a material to drive off a substantial portion of carbondioxide therefrom and oxidize at least part of the cerium, slurrying theroasted material in water, and treating the slurry with an acid-forminggas so as to dissolve the rare earth metal values of the material andform a precipitate of rare earth fluoride.

17. The process of extracting rare earth metal values from a materialrich in a substance selected from the group consisting of bastnasite andcerium-containing rare earth fluocarbonates which comprises the steps ofroasting such a material to drive ofl a substantial portion of carbondioxide therefrom and oxidize at least part of the eerie cerium,slurrying the roasted material in water, and treating the slurry withsulfur dioxide so as to dissolve the rare earth metal values of thematerial and form a precipitate of rare earth fluoride.

References Cited in the file of this patent UNITED STATES PATENTS 'IhewsMar. 16, 1926 OTHER REFERENCES Yoshiga et al.: Chemical Abstracts, vol.47, col. 7173(0), abstracted from Japan. 2266 (1952), June 18.

Browning: Introduction to the Rarer Earth Elements, pub. by John Wileyand Son, Inc., N.Y., 1914, page 43.

Hopkins: Chemistry of the Rarer Elements, pub. by D. C. Heath and Co.,NY. 1923, page 98.

Levy: Rare Earths, pub. by Longmans, Green and Co, N.Y., 1924, page 154.

Mellor: Comprehensive Treatise on Inorganic and Theoretical Chemistry,vol. 5, pages 521, 522, 545 and 564 (1924).

9. THE PROCESS OF EXTRATING RATE EARTH METAL VALUES FROM A MATERIAL RICHIN A SUBSTANCE SELECTED FROM THE GROUP CONSISTING OF BASTNASITE ANDCERIUM-CONTAINING RARE EARTH FLUOCARBONATES WHICH COMPRISES THE STEPS OFROASTING SUCH A MATERIAL TO DRIVE OFF A SUBSTANTIAL PORTION OF CARBONDIOXIDE THEREFROM AND OXIDIZE AT LEAST PART OF THE CERIUM, TREATING THEROASTED MATERIAL WITH A DILUTE NONREDUCING ACID SO AS TO DISSOLVE THERARE EARTH METAL VALUES OF THE MATERIAL, AND ADDING A WATER SOLUBLEFLUORIDE TO THE RESULTING SOLUTION OF RARE EARTH METAL VALUES TO OBTAINAN EASILY FI RABLE PRECIPITATE OF RARE EARTH FLUORIDE.